Center
a rack in the oven and preheat to 300 degrees. Line a large roasting
pan with a double thickness of paper towels, then place eight 4-ounce
or six 6 ounce custard cups, ramekins, or pot de creme cups in the pan.

Pour cream and milk together and warm them in the microwave or in a saucepan over medium heat; set aside

Measure out 1/4 cup of sugar and set aside.

Heat
a medium heavy-bottomed saucepan over med-high heat and sprinkle in 2
tablespoons of sugar from the remaining 1/2 cup of sugar.As soon as the
sugar melts and starts to caramelize, stir. When the color is uniform,
stir in another 2 tablespoons of sugar and continue to stir until it is
melted and colored. Continue adding the sugar 2 tablespoons at a time.
When the sugar is a deep amber, almost a mahogany color, standing away
from the pan, so you don't get splattered, add the warmed cream/milk.
The mixture will bubble furiously and may seize, but don't panic, just
keep stirring until it smooths out. Remove pan from the heat.

Put
the eggs, yolks, pinch of fleur de sel, and the reserved 1/4 cup of
sugar in a mixing bowl and whisk until pale and slightly thick. While
still whisking, drizzle in a little of the caramel liquid. This will
temper the eggs so you don't end up with scrambled eggs. Whisking all
the while, slowly pour in the remaining liquid. If there is any foam on
top of the custard, skim off with a spoon. The foam will cause craters
on the top of the custard as it bakes.

Arrange
custard cups in a small roasting pan, leaving an even amount of space
between the cups, and fill each cup nearly to the top with the custard
mixture. Carefully slide the pan into the oven; then, using a pitcher,
fill the roasting pan with enough hot water to come halfway up the
sides of the cups. Cover the pan with plastic wrap (don’t worry—it can
stand the heat) and poke two holes in two diagonally opposite corners.
Bake the custards for about 35-40 minutes, or until the edges darken
ever so slightly and the custards are set but still jiggle a little in
the center when you shake them gently.

Remove
the pan from the oven and let the custards sit in the water bath for 10
minutes. Peel off the plastic wrap, lift the cups out of the water and
cool the custards in the refrigerator. (The pots de creme can be
prepared a day ahead and, when cool, covered with plastic wrap and
stored in the refrigerator.)

To serve:
The pots de creme are at their best at room temperature, so remove them
from the refrigerator and keep them on the counter for about 20 minutes
before serving. Sprinkle a little fleu de sel or sea salt on the tops
of the custard.